Docs: docker, rustup, accounts

[fadeev]

• [x] Prerequisites.
  • [x] Docker. It's fair to assume, that most people will be using Beaker with Local Osmosis. Makes sense to add Docker into prerequisites, so that a user has everything to go through a tutorial
  • [x] Rust. Pretty obvious, but a link to https://www.rust-lang.org/tools/install wouldn't hurt.
• [x] rustup target add wasm32-unknown-unknown has to be executed before beaker wasm deploy
• [x] Accounts. In the frontend section adding a link to local Osmosis accounts with a short description of how to add them in Keplr might be useful for devs new to Cosmos.
• [x] Add doc for type gen

[iboss-ptk]

sounds good! thanks for suggestion :D

[iboss-ptk]

for rustup target add wasm32-unknown-unknown, it's now auto detect and install if not exist (#81)